systemd Developer Lennart Poettering lennart@poettering.net sysctl.d 5 sysctl.d Configure kernel parameters at boot /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf At boot, systemd-sysctl.service8 reads configuration files from the above directories to configure sysctl8 kernel parameters. The configuration files contain a list of variable assignments, separated by newlines. Empty lines and lines whose first non-whitespace character is # or ; are ignored. Note that both / and . are accepted as label separators within sysctl variable names. kernel.domainname=foo and kernel/domainname=foo hence are entirely equivalent. Each configuration file shall be named in the style of program.conf. Files in /etc/ override files with the same name in /usr/lib/ and /run/. Files in /run/ override files with the same name in /usr/lib/. Packages should install their configuration files in /usr/lib/. Files in /etc/ are reserved for the local administrator, who may use this logic to override the configuration files installed by vendor packages. All configuration files are sorted by their filename in lexicographic order, regardless in which of the directories they reside. If multiple files specify the same variable name, the entry in the file with the lexicographically latest name will be applied. It is recommended to prefix all filenames with a two-digit number and a dash, to simplify the ordering of the files. If the administrator wants to disable a configuration file supplied by the vendor, the recommended way is to place a symlink to /dev/null in /etc/sysctl.d/ bearing the same filename. # Set kernel YP domain name kernel.domainname=example.com systemd1, systemd-sysctl.service8, systemd-delta1, sysctl8, sysctl.conf5